The present invention relates in general to testing echo cancellers in telecommunication systems, and, more specifically, to individually testing echo cancellers for individual subscriber terminals without directly connecting to individual echo cancellers.
Due to impedance mismatches in transmission line terminations and due to transmission delays within telephone systems, electrical signal reflections (i.e., echoes) can be inadvertently created in telephone transmissions. To avoid a degradation in the voice or data signals, echo cancellers are typically deployed in central offices for each individual subscriber line connection (an individual line often being referred to as a DS-0). Echo cancellers most often use digital signal processing and are typically integrated within communication system components such as the codecs that interface between an analog terminal and a public telephone network.
As telecommunications networks increase in size and complexity, the importance of accurate and timely testing of existing and new equipment becomes great. In order to provide competitively priced service, however, the costs of testing and maintenance need to be kept low. The amount and types of test equipment, set-up times, and test procedures used by conventional echo canceller testing have resulted in high costs and slow performance. In a typical prior art procedure, for example, each DS-0 has been separately broken-out physically at a D Bank with media simulators and digital cross-connects being connected to each. Such a process has a long set-up time and is labor intensive.
Prior test equipment and methods have also been limited with respect to the types of tests and test signals that could be generated. Thus, there has continued to be a lack of flexibility in echo canceller testing, with test equipment having to be specifically designed for narrowly defined tests.